Statistical analysis of high-frequency decimetric type III bursts

Here we report the statistical analysis of 160 isolated decimetric type III bursts, a majority of them (74%) having central frequency above 1000 MHz, observed in 8 flares by the spectrometer Phoenix. The most important findin g of the detailed analysis is: 67% of all the bursts are reverse slope, 38% normal and 5% bi-directional. Also, we obtained the following results: (a) the best fits for the average half power duration and for the average drif t rate as a function of frequency are given by t(1/2)=1.7x10(4)f(-0.60) and =(0.09 +/- 0.03)f((1.35 +/- 0.10)), respectively; (b) the frequency range of most of the type III bursts is less than 250 MHz; (c) the number of burs ts decreases with increasing starting frequency and flux; (d) peak flux dec reases with increasing frequency. The relations obtained fit well for highe r frequency observations. Assuming an improved density model and type III e mission at 2(nd) harmonic, the beam parameters of type III bursts are deter mined.